Aramco Research Center Detroit
Aramco Research Center Detroit
Zhang Y.,Aramco Research Center Detroit |
Pei Y.,Aramco Research Center Detroit |
Engineer N.,Aramco Research Center Detroit |
Cho K.,Aramco Research Center Detroit |
Cleary D.,Aramco Research Center Detroit
SAE Technical Papers | Year: 2017
The current study utilized 3-D computational fluid dynamics (CFD) combustion analysis to guide the development of a viable full load range combustion strategy in a light-duty gasoline compression ignition (GCI) engine. A higher reactivity gasoline that has a research octane number (RON) of 70 was used for the combustion strategy development. The engine has a geometric compression ratio of 14.5 with a piston bowl designed to accommodate different combustion strategies and injector spray patterns. Detailed combustion optimization was focused on 6 and 18 bar gross indicated mean effective pressure (IMEPg) at 1500 rpm through a Design of Experiments approach. Two different strategies were investigated: (a) a late triggering fuel injection with a wide spray angle (combustion strategy #1); and (b) an early triggering fuel injection with a narrow spray angle (combustion strategy #2). Combustion strategy #1 preferred a higher swirl ratio, while a lower swirl ratio was more desired for combustion strategy #2. At 6 bar IMEPg, high efficiency clean GCI operation can be achieved using both strategies. When increasing the engine load to 18 bar IMEPg, combustion strategy #2 was limited by excessive pressure rise rate. In contrast, by carefully balancing between premixed combustion and mixing-controlled combustion, combustion strategy #1 led to fuel-efficient mixed-mode combustion operation. By utilizing this combustion strategy, full load operation at 24 bar IMEPg was achieved while meeting all the performance requirements. Both combustion strategies favored a larger number of nozzle holes. Combustion strategy #1 generally showed a stronger preference towards higher injection pressure. Copyright © 2017 SAE International.
Kumar K.,University of Connecticut |
Zhang Y.,University of Connecticut |
Sung C.-J.,University of Connecticut |
Sung C.-J.,Aramco Research Center Detroit |
Pitz W.J.,Lawrence Livermore National Laboratory
Combustion and Flame | Year: 2015
We study the influence of blending n-butanol on the ignition delay times of n-heptane and iso-octane, the primary reference fuels for gasoline. The ignition delay times are measured using a rapid compression machine, with an emphasis on the low-to-intermediate temperature conditions. The experiments are conducted at equivalence ratios of 0.4 and 1.0, for a compressed pressure of 20. bar, with the temperatures at the end of compression ranging from 613. K to 979. K. The effect of n-butanol addition on the development of the two-stage ignition characteristics for the two primary reference fuels is also examined. The experimental results are compared to predictions obtained using a detailed chemical kinetic mechanism, which has been obtained by a systematic merger of previously reported base models for the combustion of the individual fuel constituents. A sensitivity analysis on the base, and the merged models, is also performed to understand the dependence of autoignition delay times on the model parameters. © 2015 The Combustion Institute.
Algunaibet I.M.,Saudi Aramco |
Voice A.K.,Aramco Research Center Detroit |
Kalghatgi G.T.,Saudi Aramco |
Babiker H.,Saudi Aramco
Fuel | Year: 2016
Gasoline compression ignition (GCI) engines could be more efficient than most advanced SI engines while running on lower octane fuel. GCI engines may utilize a mixture of different fuels and fuel components such as gasoline and diesel or diesel and naphtha. The risks and hazards associated with such mixtures must be studied to ensure safe fuel storage, shipping and dispensing. In this work, flash point and vapor pressure measurements of different binary multi-component hydrocarbon mixtures are presented along with calculated lower and upper flammability limits. An equation has been developed to correlate flash point with other fuel properties. The flash point of a mixture approaches the flash point of the more volatile component, falling rapidly in some cases, as the more volatile component concentration increases. Vapor pressure is inversely related to flash point for a given mixture. Diesel/light straight run naphtha mixtures and diesel/gasoline mixtures exhibit similar flash point versus vapor pressure trends. Flammability limits were calculated using Le Chatelier's Mixing Rule and modified Burgess-Wheeler Law. Hydrocarbon mixtures have similar lower and upper flammability limits over a range of temperatures. The vapor pressure of fuels and fuel blends has been used to determine the safe operating region as a function of blending formula and temperature. This work demonstrates that normal butane can be used to formulate blends of gasoline and naphtha with diesel, which are safe to handle and meet seasonal vapor pressure requirements. © 2016 Elsevier Ltd. All rights reserved.